Try to reinstall/update your driver by going on the Dell support website.
Have you reinstalled your Windows XP operating system ? If not, you should. Dell installs so much useless softwares that slow down the computer. I have also a Dell Insprion 6400 ( the canadian version of the E1505 ) and I can tell you that there is a lot of useless stuff.
I got a Dell e1505 around a month ago and I am in general very pleased with it. About the only thing I am not pleased with is every time I restart the computer the pointer speed goes back down the default speed. So everytime I start it up I have to go back into the control panel and speed it back up so I don't have to move my finger across the touchpad 50 times to get the pointer across the screen. If anybody could tell me what's going on I would appreciate it.